The invention relates to gloss measuring devices and more particularly to a simple, inexpensive instrument for measuring the gloss of coatings.
Gloss is a measure of the light that is reflected from a surface. Gloss is usually determined according to ASTM D 523, Specular Gloss. For coatings, the 60-degree gloss is typically measured. The light reflected at 60 degrees from the vertical is compared to the light incident at 60 degrees from the vertical, and the ratio is expressed as a percentage of the reflection that would be obtained from polished black glass.
The amount of light reflected from a coated surface is very dependent on the angle of reflection. Viewed at very low angles (or at angles approaching 90 degrees as measured from the perpendicular), flat coatings or even roadway surfaces may give mirror-like reflections. Thus, for flat coatings, the 85-degree gloss is measured, and for high gloss coatings, the 20-degree gloss may be measured. Portable photometric instruments presently used for each of these measurements are expensive.
There are a number of devices available for measuring gloss, all of which are complicated and expensive apparatus having both electrical and mechanical components. Prior to the present invention, there was no good way of measuring in the field without expensive instrumentation, the gloss of a formulated coating.